build: pywrap: Add deps on common.i into pywrap.mk

Now all wrappers are rebuild when common.i is changed.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
pywrap: Add default typemap for callback=NULL

Now all callback args have default NULL value.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
demos: py_simple: Drop None callback parameters.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
filters: Linear: Run one thread on in-place filter

If filter is run in-place (src == dst) the filter cannot run in more
than one thread (as threads would override values read by other
threads).

This patch changes the Linear Convolution filters to default to one
thread if in-place usage is detected instead of the ASSERTS()

Also update linear convolution docs.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
filters: Convolution; Minor cleanup.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
filters: Blur: Hotfix the GaussianBlurAlloc() case

The code wrongly passed src as src and dst as dst to both vertical and
horizontal convolution, which is wrong in case src != dst because the
result from the first convolution is always lost.

Workaround this by passing dst as both src and dst to the second one.
The drawback is that the second convolution would not run in multiple
threads but at least it yields correct result.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
doc: Work on python filter docs (add GaussianBlur)

* Add Gaussian blur example images generator
  (gfxprim must be installed to regenerate the images)

* Add Gaussian blur python example + docs

Signed-off-by: Cyril Hrubis <metan@ucw.cz>